1. Field Of The Invention
This invention directs itself to pinch valve systems for coupling with fluid flow lines. In particular, this invention directs itself to a pinch valve system which is a replacement for and interchangeable with ball, plug and gate type valves. Still further, this invention directs itself to pinch valve systems having a high temperature and pressure operating capacity and long service life. More in particular, this invention pertains to a pinch valve system having a flexible-walled sleeve wherein a pair of transverse folds are provided to allow the sleeve to be pinched closed without substantial stretching of the sleeve wall. Further, this invention directs itself to a pinch valve system wherein the valve body includes a pair of circular recesses for receiving the folded portions of the flexible-walled sleeve to permit the sleeve to be maintained in contiguous contact with the interior wall surface of the valve body.
2. PRIOR ART
Pinch valves are well known in the art. The best prior art known to the Applicant include U.S. Pat. Nos. 3,640,354; 3,965,925; 4,092,010; 4,108,418; 4,111,391; 4,191,358; 4,205,697; 4,310,140; 4,330,101; 4,345,735; 4,372,528; 4,642,833; and, 4,824,072.
Pinch valve systems are widely used because of their simplicity and low cost. In many prior art systems the pinch valve includes a straight tubular sleeve, which when pinched to close the valve causes stretching of the sleeve member. The stretching of the sleeve member is detrimental to the life of the sleeve and limits the use of reinforced sleeves, those sleeves having reinforcing cords or fibers incorporated therein. Reinforced sleeves are those wherein a fiber such as fiberglass, Kevlar, carbon fibers and the like, are utilized to strengthen the tubular sleeve for operation at high pressures and temperatures. Since the fibers are inelastic, they are usually woven to allow for some displacement in the direction in which the sleeve is to be stretched, but this is at a cost of sacrificing some of the strength which the reinforcing cord would otherwise provide.
Since the stretch of the reinforced sleeve is substantially limited, even with a stretch accommodating weave of the fibers, prior art systems require that the overall sleeve length must be made several times greater than the diameter of the sleeve if reasonable service life is to be achieved. Since the sleeve is typically coupled to the valve body on opposing ends, the longer the distance between the pinch point and the point of coupling to the valve body, the less stretch will be imposed on the sleeve. Thus, most manufacturers provide pinch type valves having a sleeve length on the order of three times their inner diameter. Due to this characteristic of prior art pinch type valves, they are typically much longer than other standard valves such as ball, gate or plug type valves, and cannot therefore be readily interchanged therewith. Thus, in applications which previously incorporated these other valve types, pinch type valves are not readily usable, without expensive modifications to the pipelines, since the pinch valves have not heretofore come in the standard lengths, as provided with these other valve types. The instant invention overcomes this deficiency by providing a flexible-walled tubular sleeve which can be substantially shorter in length than incorporated in prior art systems, and operated without substantial stretching of the sleeve wall. The pinch valve of the instant invention thereby being produceable in the dimensions which provide for interchangeability with ball, gate and plug type valve systems.
In other prior art systems such as that disclosed in U.S. Pat. No. 4,192,358 there is provided a flexible-walled sleeve having a plurality of transversely shaped folds of sufficient material to prevent over-extension of the sleeve when pinched. However, these plurality of folds form a corrugated configuration which consumes cross-sectional flow area and provides an irregular surface pattern which will introduce turbulence into the fluid flow passing through the valve structure. Such valve structures are particularly susceptible to damage caused by cavitation, or abrasion, when slurries are flowing therethrough.